SnuKKi-nr : O.steoi.ogv ok thk Hkrodionks. 193 



it passes are here more niassi\e in onler to contain that part of 

 the coril fVoni which the sacral i)lexus emanates. The foramina from 

 which they issue, on either side, are double, being placed one above 

 another. This obtains also in at least four of the vertebr;e beyond 

 these and one other behind, making eight in all whose sides are pierced 

 by these double foramina. 



Apophysial abutments are again thrown out to anchylos^ with the 

 pelvic bones above them, by the thirty-second to the thirty-seventh 

 vertebra inclusive. The longest pair of these come from the thirty- 

 second vertebra, and thereafter grow gradually shorter as we proceed 

 backwards. 



The " brim of the pelvic basin " is continuous with the processes of 

 the thirty-sixth vertebra posteriorly, while anteriorly it merges with 

 the posterior border of the transverse processes of the twenty-eighth. 

 This boundary has a rounded and well-defined border in the Great 

 Blue Heron, and is more or less determinable in the majority of birds. 

 When viewed from above, this bone presents a strikingly smooth and 

 unbroken superficies — it is scarcely marked by either crests or ridges, 

 and in my specimen only two pairs of inter-apophysial foramina are 

 seen, these being between the last two vertebree. 



Anteriorly, in the median line, the neural spine of the twenty-fourth 

 vertebra is observed to project as a tuberous and notched process. 



For some little distance back of this, the ilia meet on either side of 

 this common neural crest sealing over the ilio-neural grooves and mak- 

 ing one rounded summit for this part of the bone. 



The anterior margins of the ilia are notched and scalloped, and 

 bordered by a somewhat deep and slightly raised emargination. Where 

 these bones are broadest in front, the . lateral edges are quite sharp, 

 but as the pelvis contracts in width as we near the acetabula they be- 

 come rounded and smooth. The iliac surface, on either side, thus 

 bounded, is at first directed upwards and outwards, but as it approaches 

 either acetabulum, this surface gradually comes to look almost directly 

 outwards. Ilio-neural grooves exist between the anterior forks of the 

 gluteal ridges for some little distance, before these latter and well 

 defined crests are lost anteriorly (Fig. 13). 



Few traces or markings are left upon the inner margins of the 



postacetabular surfaces to define the boundaries which originally 



existed between the vertebrae and the iliac bones ; they are best seen 



l)ehind. For the most part though, the pelvic roof has become in 



13 



